Delayed arming safety fuse



July 5, 1955 H. E. THOMAS ET AL 2,712,284

2 DELAYED ARMING SAFETY FUSE Filed June 19, 1951 2 Sheets-Sheet 1 Fig. l

Hurmld E- ThEllTLllB Francis P. Eilhunly 7W, amm JMK W July 5, 1955 H. E. THOMAS ET AL DELAYED ARMING SAFETY FUSE 2 Sheets-Sheet 2 Filed June 19 1951 grwvwfo'w Hurmld E- Thmmua Frunnifi 1 1 Gill-11:1 01y @W, a W g DELAYED ARMING SAFETY FUSE Hamid E. Thomas, Alexandria, Va., and Francis P. Gilhooly, Huntsville, Ala.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to delayed arming safety fuzes for explosive projectiles such as shells, rockets and the like.

A defect sometimes found in projectiles of the type described is the tendency to burst prematurely. Such explosions are undesirable because they may either cause extensive damage at the discharge point or destroy the missile in flight before it reaches its target. These explosions are usually caused by premature action of the fuze. The primary object of our invention is therefore provision of a fuze that will not prematurely detonate the projectile in which it is placed. These unwanted bursts are frequentiy caused by the element that is responsible for the proper detonation of the projectile, that is, by the firing pin. A fuze cannot be detonated by the firing pin until it is armed. A second object of the invention is therefore provision of a mechanism that will positively delay the arming of a fuze until the projectile has at least left the launching area. Other objects of the invention will appear from the description following.

Our invention consists in brief of a delay mechanism built around a Zig-zag branch groove forming a race set into the body of the fuze. This race presents connected initial and final positions, on the same internal circuit.- ference of the fuze body and set at a predetermined are from each other, to a control pin. The pin runs in a slot cut into the inner of two concentric sleeves and is fixed to the outer. body of the fuze and is controlled by a spring. When the fuze is accelerated the inertia of this outer sleeve causes it to be set back on its spring, carrying the pin with it. The race forces the pin to follow a zig-zag course. The inner sleeve is fixed longitudinally but can rotate in the fuze body and therefore oscillates with the movement of the pin. A notch in the inner or arming sleeve is adapted to permit a second spring to force a shutter carrying the detonating charge into such a position that the latter can be actuated by the firing pin. In this position the shell is armed. The recess appears under the firing mechanism when the arming sleeve has been rotated the predetermined are between the initial and final position set into the race. The race, lengthened as desired by the zig-zags, basically determines the exact time when the fuze becomes armed.

We are aware that delays in the form of a race have been incorporated in fuzes previously. U. S. Patent 1,053,857 to Nordenfelt shows an example of such a race. British Patent 489,020 teaches the use of a groove as a guide for a safety bolt. A somewhat similar groove is shown by French Patent 695,100. A smooth race is shown in German Patent 359,102. Other grooves have been used in several German military fuzes, for example the AZRZ and the ZZRI. As a consequence we do not claim to be the first to utilize grooves as time delays in fuzes. We do claim to be the first to utilize the particular The outer sleeve is short compared to the I features shown by our drawings which give a positive safety as well as a delay in the arming of our fuze. Our construction therefore ettects a result not possible in and not contemplated by the above-mentioned prior art.

A more detailed understanding of our invention may be obtained from a consideration of the drawings in which:

Figure 1 is a longitudinal section of one embodiment of our invention;

Figure 2 is another longitudinal section taken along line 22 of Figure 1;

Figure 3 is a transverse cross-sectional view taken along the line 33 of Figure 1;

Figure 4 is a detailed view of an arming sleeve of our invention;

Figure 5 is a view illustrating the position of the arming elements at the beginning of the arming process;

Figure 6 is a view showing the position of the arming elements at the end of the arming period; and

Figure 7 is a developed plan view of the delay race incorporated in the embodiment of Figure 1.

Figures 8 through 14 represent a modified version of our invention in which:

Figure 8 is a longitudinal axial section, corresponding to Figure 1, of the second embodiment of our invention;

Figure 9 is a cross sectional view taken along line 99 of Figure 8;

Figure 10 is a side view of the support for the arming mechanism used in the embodiment of Figure 8;

Figure 11 is a cross sectional view of the arming mechanism itself taken along the line 1111 of Figure 8;

Figure 12 is a rear view of the plate carrying the arming mechanism;

Figure 13 is a view of the modified arming sleeve; and

Figure 14 is a developed plan view of the modified delay race.

Figures 1 through 7 show a cylindrical fuze body which has a nose 22 fastened thereto through threads 21.. Fuze body 20 can be fitted into a projectile by means of threads 23. A shield 25 is connected to nose 22 by fastener 26. Inside the shield 25 two contact elements 27 and 23, joined by threads 29, are slidably held in place by firing pin support 30. Firing pin support 30 is a small metal cylinder, closed at one end but open at the other, carrying firing pin 31 on its closed end.

The open end of firing pin support 30 extends over part of a container 32 for the detonator 41. Container 32 is integral with a base plate 33 rigidly held in a groove 34 formed between fuze body 20 and nose 22 at their connecting point. Container 32 is hollow and closed by a top 35 which may be screwed to the base plate 33. Hole 36 passes through top 35 while a slot 37 penetrates the container along its side for a purpose evident hereinafter. Spring 38 between base plate 33 and the firing pin support 30 holds the latter resiliently in position.

Rotatable within container 32 is shutter 49 in the form of a short stubby cylinder. The shutter carries internally a primer 41 and, upon its external surface, fastened by screw 42, a U-shaped guard 43 for the firing pin 31. Guard 43 travels in slot 3'7 in container 32. In its normal position the guard is at one end of the slot immedi ately behind and extending along the firing pin, its flanges 44 parallel to the sides of the slot. eing slightly longer that the firing pin 31, these flanges 44 absolutely prevent contact between the pin and the shutter as long as the fuze is unarmed. Spring 33 alone might permit contact between this detonator carrying shutter and the firing pin if the fuze were dropped but guard 43 prevents such excess motion of the spring. This guard performs alsouthe function of a stop in that it prevents any rotation of the cylindrical shutter 49 except along the path of slot 37.

Extending through hole 36 in top 35 of the container 32 is projection 45 along and integral with the. axis .of

3 rotation of shutter 40. Projection has a squared portion 46 against one corner of which presses spring 47 under tension. This spring is screwed to the base plate 33. Set-back pin 48 extends slidably through the base plate into a recess 49 in shutter 40. Projection 45 is normally under pressure from spring 47 applied in such a manner that the projection, and its associated shutter 40, would rotate if it were free to do so. As long however as set-back pin 48 is in position in recess 49. movement of the shutter is impossible. Spring 50, mounted in bore 51 in the underside of base plate 33, presses against head 52 of set-back pin 48, urging it out of the recess. In the normal disarmed position of the fuze. head 52 is firmly held by arming sleeve 57. to be discussed later, and cannot be dislodged by spring 50. It may be mentioned that removal of this set-back pin 48 permits rotation of the shutter 40 and arming of the fuze. Base plate 33 carries one other element besides bore 51 integral with its under side, namely, cylindrical holder 53. This holder, symmetrical about the longitudinal axis of fuze body 20, is in contact with the container 32 on the front side of the plate. Holder 53 carries a booster charge 54.

So far there have been discussed elements chiefly associated with the nose 22. Now there will be described elements largely associated with the fuze body 20 itself.

Concentric with fuze body 20 are three cylinders retained by the butt portion 69 of the fuze body, the innermost of which, 55, extends from the rear end of the fuze body 20 to holder 53 which it contacts. This cylinder 55 forms a chamber, closed at all points except at the end contacting holder 53, in which is placed a second booster charge 56. Adjacent cylinder 55 is cylindrical arming sleeve 57 extending from the butt portion 69 of the fuze body 20 to the contact with head 52 of set-back pin 48.

Held by flange 59 on arming sleeve 57 is creep spring 58 i which resiliently holds the third concentric cylinder. inertia sleeve 60 is much shorter than arming sleeve 57 and can slide upon the latter against creep spring 58.

Arming sleeve 57, shown in detail in Figure 4, possesses two longitudinal slots 61 diametrically opposite each other and is fixed longitudinally by the butt portion 69 of the fuze body but is free to rotate therein. In each slot is carried slidably the head 63 of a pin 62. Each pin 62 extends through a hole 64 in inertia sleeve 60. The pin fits snugly into hole 64 and consequently must travel with the inertia sleeve. Each pin also extends slidably into a race 65, shown in development in Figure 7, cut into the fuze body 20. When travelling with the inertia sleeve 60 the pin 62 must move along the path determined by the race, forcing arming sleeve 57 to follow any radial movement along the fuze body which the pin makes. Arming sleeve 57 possesses two notches 66 in its front portion. These notches are of such size that the head of the set-back pin 48 will fit into them easily. Cousequently if either notch comes in position behind head 52 spring 50 will force the setback into the notch and release shutter 40. Two notches are provided to make certain that the arming sleeve is not assembled in the wrong position.

Race 65 is the timing element of our invention. Point A marked on the race is the initial position of pin 62. Point C is the final position. The number of degrees of are between A and C corresponds to the radial distance that operative notch 66 is initially set away from head 52 of set-back 48. As a consequence, when pin 62 has travelled from A to C, notch 66 has come into position behind the set-back, permitting the arming of the fuze. The length of the race determines the time required for the pin to travel between its initial and final positions. Zig-zag turns may therefore be used to lengthen the path of travel and to increase the delay incorporated in the arming. Arming sleeve 57 follows pin 62 in its travels down the race, oscillating back and forth until the pin finally reaches position C. It will be noted that the race possesses two branches, 67 and 68, joined at intermediate position B. As long as pin 62 has not reached point B, that is as long as it remains in branch 67, removal of the force impelling the pin will permit creep spring 58 to push it back to point A. Once however the pin has reached point B it can only continue travelling along branch 68. Consequently removal of the force retaining the pin at point B will allow the creep spring to push the pin to point C. Branching is therefore a safety feature incorporated in the race.

The functioning of our invention is evident from the foregoing description. When the missile containing the fuze is accelerated, inertia sleeve 60 moves back on creep spring 53 carrying pin 62 with it. As the pin moves from point A to point B in the race 65, the arming sleeve 57 r is compelled to oscillate with the turns in the race, these turns progressing radially as well as longitudinally down the fuze body. When the acceleration on the missile and the fuze is removed, the creep spring moves the pin from point B to point C, forcing the arming sleeve again to move radially with the pin. When the pin reaches C, the arming sleeve has moved through the arc separating notch 66 from set-back head 52. Spring 50 can now force setback 48 out of recess 49, removing the detent action of the set-back. Spring 47 is able to rotate shutter 40 through the distance determined by slot 37. This distance is calculated to bring the detonator 41 under firing pin 31. When the firing pin reaches this position, the fuze is armed. The acceleration necessary to cause arming can be determined from the mass of the inertia sleeve and the strength of the creep spring. The length of time this acceleration must remain operative to complete arming may be varied by lengthening or shortening the race, that is, by adding or subtracting turns from the zig-zag path. Consequently the constants of the inertia sleeve, the creep spring and the race can be' set so that arming is impossible before the projectile has cleared its launching area.

Figures 8 through 14 show an embodiment of our invention diifering in some details from that described above but built up around the same timing element, namely, the zig-zag race.

'A fuze body 20 is shown threaded to a nose 122 containing contact element 127 and firing pin support 130 resiliently connected to firing pin 131 through spring 138. Base plate 133 carries shutter and shutter protector 141 mounted on' legs 142. Shutter 140 is pivoted on plate 133 by pivot 169 located at a point near the circumference of the plate. This plate 133 is pierced by arcuate slot 151 through which extends projection 147 on arming sleeve 157. The general shape of the shutter 140 is triangular with a projection at one apex of the triangle. Projection 145 is adapted for engagement by head 148 on the projection 147 of the arming sleeve. Upon shutter 140 is a raised portion 172 in which are located primer 141 and cylindrical recess 173. Pivot 169, primer 141 and'recess 173 are located at the apices of an equilateral triangle. Spring 174 is at the pivot 169 contacting stud 175 on plate 133 and raised portion 172 on the shutter. The spring 174 is under compression between the stud and the raised portion of the shutter when the fuze is unarmed and urges the primer'lll clockwise as viewed in Figure ll into axial alinement with firing pin 131. Race presents two sections 167 and 168 to pin 62 and while shown as more or less the mirror image of race 65 (Figures 1 to 7) can be in about any configuration desired so long as the timing requirements discussed above are satisfied. The rearward portion of this embodiment of the invention is identical with that of the first embodiment except for the projection on the arming sleeve. Parts numbered alike in the drawings are identicaland serve the same purpose.

The operation of the second embodiment is much the same as that of the first. Inertia sleeve 60 is set-back along the race when the fuze is accelerated. Head 148 on the projection 147 arming sleeve reaches the position shown by the dotted lines in Figure 11 when pin 62 arrives at point C in the race 165. In this position of the head the spring 174 is free to rotate shutter 140 from the unarmed position, that is with recess 173 under firing pin 131, to the armed position where primer 141 is under the pin to be engaged and initiated thereby on impact of the projectile.

The two forms of our invention shown are obviously not the only ones in which our delay mechanism can be incorporated. In fact, we do not wish to be strictly bound by the embodiments disclosed but solely by the appended claims.

We claim:

1. In a point detonating fuse with a cylindrical body having a longitudinal axis, a rearwardly opening cupshaped support slidably mounted in the forward end of said body, a rearwardly directed centrally located firing pin secured to the closed end of said cup-shaped support, a container disposed in said body rearwardly of said firing pin having formed therein a spheroidal cavity, a shutter rotatable in said cavity from first safe position crosswise of said longitudinal axis to second armed po sition, said shutter having formed therein a diametral bore adapted to axially aline with said firing pin when said shutter is in armed position, a detonator in said diametral bore, resilient means in said body engaging said shutter and biasing same into armed position, and inertia responsive delay means in said body for releasably locking said shutter in safe position until said fuse has traveled a predetermined distance, said inertia responsive means comprising a race cut skew into the inner surface of said fuse body rearwardly of said container, an elongated arming sleeve concentric within said fuse body rearwardly of said container, said arming sleeve being fixed longitudinally relative to said fuse body and freely rotatable therein, a relatively short inertia sleeve interposed between the forward end of said arming sleeve and the race in said fuse body, a detent pin extending through the bottom of said container ha ing one end releasably locking said shutter in armed position and its other end engaging the forward end of said arming sleeve whereby said detent pin is movable to release said shutter as said arming sleeve rotates, and a pin radially extending through said inertia sleeve be ing its inner end received in a longitudinal slot in said arming sleeve and its outer end received in said race.

2. The device in claim 1 including resilient means in said fuse body surrounding said arming sleeve adapted to engage and biasing to original position said inerti: sleeve.

3. The device in claim 2 wherein the length of said race serves as a time delay, said race having irregularities in its length to advance delay in arming.

4. The device in claim 2 wherein said race determines an initial and a final position for said radial pin, said positions being set on the same internal circumference of said fuse body separated by a predetermined arcuate distance. v

5. The device in claim 4 wherein said race possesses first and second converging branches interconnected at a position intermediate said initial and final position whereby said lateral pin must travel completely-along said first branch before it can be forced along said second branch by said inertia sleeve biasing means. 5

6. The device in claim 5 including resilient means biasing said detent pin rearwardly and out of shutter locking position, the forward end of said arming sleeve having a forwardly protruding portion adapted tofabut said detent pin when said fuse is unarmed, and a recess to permit retraction of said detent pin to arm said fuse as said arming sleeve is rotated.

7. In a point detonating fuse having a cylindrical body symmetrical about a longitudinal axis, a rearwardly directed axial firing pin located forwardly in said body, a shutter in said body rearwardly of said firing pin and having a diametrally disposed detonator, said shutter and detonator being unitarily rotatable from first safe position crosswise of said longitudinal axis to second armed position to aline with said firing pin, resilient means in said body biasing said shutter to armed position, a detent pin in said body releasably locking said shutter in safe position, resilient means biasing said detent pin to shutter releasing position, and inertia responsive delay arming means operative only when an inertia member has traveled a predetermined distance relative to an arming sleeve to permit movement of said detent pin to shutter releasing position, said inertia responsive means comprising a race cut skew into the inner surface of said cylindrical body rearwardly of said shutter, an inertia sleeve concentric with and slidable within said cylindrical body, a lateral pin having one end traveling in said race and actuable by said inertia sleeve, an inner elongated arming sleeve concentric within said inertia sleeve rotatable with respect thereto and longitudinally fixed relative to said cylindrical body, said inner sleeve being engaged by the inner end of said lateral pin whereby skew motion of the lateral pin is translated to rotation of said inner sleeve, said inner sleeve having a recess for receiving said detent pin as said inner sleeve rotates whereby said shutter is released to move to armed position.

8. The device in claim 7 including resilient means about said inner sleeve abutting and constantly biasing said inertia sleeve forwardly in said cylindrical body.

9. The control device of claim 8 in which said race contains irregularities in its course to lengthen said course.

10. In a point detonating fuse having a cylindrical body symmetrical about a longitudinal axis, a rearwardly directed axial firing pin located forwardly in said body. a shutter in said body rearwardly of said firing pin and having a detonator disposed therein, said shutter being rotatable to move said detonator from a first safe position to a second armed position in axial alinernent with said firing pin, resilient means in said body biasing said shutter to armed position, detent means in said body releasably locking said shutter in safe position, and inertia responsive delay arming means operably engaging said detent means and operative only when an inertia member has traveled a predetermined distance relative to an arming sleeve to effect movement of said detent means to shutter releasing position, said inertia responsive means comprising a race cut skew into the inner surface of said cylindrical body rearwardly of said shutter, an inertia sleeve concentric with and slidable within said cylindrical body, a lateral pin having one end traveling in said race and actuable by said inertia sleeve, an inner elongated arming sleeve concentric within said inertia sleeve rotatable with respect thereto and longitudinally fixed relative to said cylindrical body, said inner sleeve being engaged by the inner end of said lateral pin whereby skew-motion of the lateral pin is translated to rotation of said inner sleeve, said inner sleeve having operative engagement with said detent means whereby said latter means moves to shutter releasing position as said inner sleeve rotates to release said shutter for movement to armed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,053,857 Nordenfelt Feb. 18, 1913 FOREIGN PATENTS 13,283 Great Britain of 1906 312,796 Italy NOV. 25, 1933 620,875 Great Britain Mar. 31, 1949 

